This invention relates to a photosensitive member for electrophotography, in particular, a photosensitive member having a photosensitive layer containing a phthalocyanine compound.
Known photosensitive materials for forming a photosensitive member include inorganic photoconductive materials such as selenium, cadmium sulfide or zinc oxide.
These photosensitive materials have many advantages such as low loss of charges in the dark, an electrical charge which can be rapidly dissipated with irradiation of light and the like. However, they have disadvantages. For example, a photosensitive member based on selenium is difficult to produce, has high production costs and is difficult to handle due to inadequate resistivity to heat or mechanical impact. A photosensitive member based on zinc oxide, or cadmium sulfide has defects such as its unstable sensitivity in a highly humid environment, loss of stability with time because of the deterioration of dyestuffs added as a sensitizer by corona charge and fading with exposure.
Many kinds of organic photoconductive materials such as polyvinylcarbazole and the like have been proposed. These organic photoconducitive materials have superior film forming properties, are light in weight, etc., but inferior in sensitivity, durability and environmental stability compared to the aforementioned inorganic photoconductive materials.
Various studies and developments have been in progress to overcome the above noted defects and problems. A photosensitive member containing a phthalocyanine compound as a photoconductive material has been proposed in, for example, Japanese Patent Laid-Open Nos. 38543/1975, 95852/1986, 64040/1978, 83744/1988 and the like, because a phthalocyanine compound has been found to have excellent photoconductivity in the range from visible light region to near infrared light region.
Further, such a phthalocyanine-containing photosensitive member has been studied for its application to an electrophotographic printer with a semiconductor laser or a light emitting diode as a light sourse.
With respect to a photosensitive member, a monolayer type and a laminated type are known. A photosensitive member of a mono-layer type is formed by applying a dispersion solution of a phthalocyanine compound, if necessary, a charge transporting material in binder resin onto an electrically conductive substrate to be 5-20 .mu.m in thickness after dried. In order to form a photosensitive member of a laminated type, a phthalocyanine is deposited or a phthalocyanine is dispersed in a binder resin, to form a charge generating layer of 0.01-1 .mu.m in thickness on an electrically conductive substrate. Then, a charge transporting layer of 10-30 .mu.m in thickness is formed on the charge generating layer.
In the case of a function-divided photosensitive member of a laminated type containing a phthalocyanine, a charge generating function and a charge transporting function are divided by a different material. A charge generating material and a charge transporting material can be selected from various kinds of materials to improve sensitivity, charging properties, surface properties and the like required for a photosensitive member. Therefore, such a function-divided photosensitive member of a laminated type is utilized generally.
With respect to a phthalocyanine compound, the one of unstable crystal type is usually used because it effects higher sensitivity than that of stable crystal type.
But, a phthalocyanine compound of unstable crystal type has a lower electrical resistance than stable crystal type. Therefore, a photosensitive member containing a phthalocyanine compound of unstable crystal type has such problems that chargeability is poor and that a surface potential decreases when repeatedly used.